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A Curtin University-led international study has solved the mystery of how the skin of a fossilized fish was able to be preserved for 52 million years, extending our understanding of how even the most delicate of biological material can survive deep time.

The researchers examined a remarkably well-preserved specimen of Diplomystus dentatus complete with fossilized skin and scales, found in the "Fossil Basin" region of Wyoming in the United States of America. Their article, "Fossilization of fish soft tissue in oxidative microniches of anoxic sediments," was in Environmental Microbiology.

Despite being in an oxygen-elevated micro-environment, which would normally cause tissues to decay, the team discovered the initial degradation of the fish's fatty skin also led to an environment where phosphate minerals could form and rapidly replace organic material—leading to fossilization.

As the skin broke down, it released fatty acids and hydrogen ions, altering the surrounding chemistry in a way that favored phosphate preservation by effectively blocking the usual carbonate deposits which would have otherwise caused the tissues to decay.

Lead author Dr. Amy Elson from Curtin's School of Earth and Planetary Sciences said the findings challenged long-held assumptions about the role of oxygen in fossilization.

"We usually think of low-oxygen, or 'anoxic,' conditions as essential for preserving soft tissues because oxygen promotes decay," Dr. Elson said.

"But this case shows that even in oxygen-rich settings, unique chemical conditions can protect delicate tissues for tens of millions of years.

"Our work provides new insights into why some fossils preserve incredible detail while others do not."

Senior author, WA-Organic and Isotope Geochemistry Center Founding Director and ARC Laureate Fellow Professor Kliti Grice said the study had wider implications beyond advancing paleontological science.

"This discovery broadens our understanding of fossilization and the chemical conditions that allow biological materials to persist," Professor Grice said.

"Beyond reconstructing Earth's evolutionary history, understanding these processes could inspire new ways to preserve biological materials in medicine, guide exploration for energy and mineral resources and improve methods for locking away carbon in sediments to help tackle climate change.

"It shows how looking back deep into Earth's past can help address challenges we face today and in the future."